Hard Hat with Impact Performance Materials

ABSTRACT

A hard hat, including an outer shell constructed of material designed to provide protection to a wearer in extreme environmental conditions is provided. In one embodiment, the wall thickness of the outer shell is reduced to minimize the weight and/or bulk of the hard hat.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

The present application is a continuation of International Application No. PCT/US2022/034039, filed on Jun. 17, 2022, which claims the benefit of and priority to U.S. Provisional Application No. 63/212,334, filed on Jun. 18, 2021, which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of protective equipment. The present invention relates specifically to various hard hat designs constructed with materials to provide added impact protection to a user's head.

SUMMARY OF THE INVENTION

One embodiment of the invention relates to a hard hat including an outer shell. The outer shell includes an exterior surface and an interior surface that defines a cavity sized to receive the head of an operator. The outer shell further includes a brim portion defining a lower circumference extending along the exterior surface and an impact protection layer positioned within the cavity. The outer shell is formed from a material that includes a yield strain greater than 9%.

Another embodiment relates to a hard hat including a shell formed from a rigid material. The shell includes an exterior surface and an interior surface that defines a cavity sized to receive the head of an operator. The shell further includes a crown portion positioned in a central area of the hard hat surrounding a center point and a bottom portion defining a lower circumference extending along the exterior surface. The shell material includes a tensile strength of greater than 35 MPa.

Another embodiment of the invention relates to a hard hat including an outer shell formed from a rigid material. The outer shell includes an exterior surface and an interior surface defining a cavity sized to receive the head of an operator. The outer shell further includes a crown portion positioned in a central area of the hard hat surrounding a center point, a bottom portion defining a lower circumference extending along the exterior surface, and an impact protection layer positioned within the cavity. The outer shell material includes a multi-axial impact toughness greater than 27 joules.

Another embodiment of the invention relates to a hard hat including an outer shell formed from a rigid material. The outer shell includes an exterior surface and an interior surface that defines a cavity sized to receive the head of a wearer. In some embodiments, an impact protection layer is positioned within the cavity. In a specific embodiment, the outer shell includes a minimum wall thickness. In a specific embodiment, the outer shell material includes a yield strain of at least 9%, specifically between 13% and 15%. In a specific embodiment, the outer shell material includes a tensile strength of at least 35 MPa, specifically between 50 and 60 MPa. In a specific embodiment, the outer shell material includes a yield strain greater than 5%, specifically between 10% and 12%. In a specific embodiment, the outer shell material includes a strain to failure greater than 17%, specifically between 70% and 80%. In a specific embodiment, the outer shell material includes a tensile strength greater than 65 MPa, specifically between 82 and 92 MPa. In various embodiments, the total weight of the outer shell is less than a maximum weight.

Another embodiment of the invention relates to a hard hat including an outer shell formed from a rigid material. The outer shell includes an exterior surface and an interior surface that defines a cavity sized to receive the head of a wearer. The outer shell further includes a crown portion and a bottom or brim portion defining a lower circumference of the hard hat. In a specific embodiment, the outer shell includes a minimum wall thickness. In a specific embodiment, the outer shell material includes a notched izod impact strength of at least 450 joules/meter, specifically between 700 and 750 joules/meter. In another specific embodiment, the outer shell material includes a notched izod impact strength greater than 160 joules/meter specifically between 650 and 680 joules/meter. In another specific embodiment, the outer shell material includes an impact toughness of at least 27 joules, specifically between 65 and 75 joules.

Additional features and advantages will be set forth in the detailed description which follows, and, in part, will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary.

The accompanying drawings are included to provide further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments and, together with the description, serve to explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

This application will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements in which:

FIG. 1 is an exploded view of a hard hat, according to an exemplary embodiment.

FIG. 2 is a plot of the yield strain of an outer shell material of the present disclosure plotted relative to the yield strain of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 3 is a plot of the tensile strength of an outer shell material of the present disclosure plotted relative to the tensile strength of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 4 is a stress-strain curve of an outer shell material of the present disclosure plotted relative to the yield strain of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 5 is a plot of the yield strain to failure of an outer shell material of the present disclosure plotted relative to the yield strain to failure of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 6 is a plot of the tensile strength to failure of an outer shell materials of the present disclosure plotted relative to the tensile strength to failure of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 7 is a plot of impact strength of an outer shell materials of the present disclosure plotted relative to the impact strength of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 8 is a plot of impact strength of an outer shell materials of the present disclosure plotted relative to the impact strength of two alternative exemplary outer shell materials, according to an exemplary embodiment.

FIG. 9 is a plot of the multi-axial impact toughness of an outer shell materials of the present disclosure plotted relative to the multi-axial impact toughness of two alternative exemplary outer shell materials, according to an exemplary embodiment.

DETAILED DESCRIPTION

Referring generally to the figures, various embodiments of a hard hat including an outer shell material designed to provide improved protection from safety hazards (e.g. falling objects) are shown. In general, Applicant has determined that by constructing the outer shell from one or more of the innovative materials discussed herein, hard hats can demonstrate improved properties (as discussed and quantified below) over a wider range of temperatures and impact speeds found in a construction setting so that protection is provided in more extreme environmental conditions. Thus, Applicant has identified a variety of innovative materials discussed herein that provide for a unique and innovative combination of material properties that Applicant has identified provided significant performance improvement when used in a hard hat/helmet application. Further, in typical hard hat designs the requisite structural performance is provided by having a relatively thick, bulky and/or heavy outer hard shell. In some embodiments, Applicant has designed a hard hat outer shell that utilizes the innovative materials discussed herein to provide improved structural performance allowing for the design of a hard hat shell with lower wall thickness and/or lower weight. Such design improvements allow for a helmet that provides a high level of protection while at the same time allowing for more user comfort, which is particularly important in the context of a protective work helmet/hard hat in which user's may wear the device for many hours spanning a workday/shift.

Referring to FIG. 1 , an exploded view of a hard hat 10 is shown according to an exemplary embodiment. Hard hat 10 includes an outer shell 12 formed from a rigid material, such as a rigid polymer material. Outer shell 12 includes a crown portion 13 and a bottom or brim portion 15 defining a lower circumference of hard hat 10 extending along an exterior surface of outer shell 12. The crown portion is positioned in a central area of the hard hat surrounding a center point. Outer shell 12 further includes an interior surface. In one embodiment, hard hat 10 includes an impact protection layer 14 supported within outer shell 12 and specifically positioned within the interior surface that defines a cavity sized to receive the head of a wearer or operator. Details of the various embodiments of outer shell 12 are discussed in more detail below. Hard hat 10 includes a suspension system 16 and a chin strap 18 to support and secure hard hat 10 to a user's head. Hard hat 10 also includes various layers of padding 20 to provide increased comfort to the wearer.

Referring to FIGS. 2-8 , a variety of material properties for an innovative material from which outer shell 12 is formed are shown (see e.g., FIG. 1 ). These properties are shown compared to select conventional hard hat materials. Applicant has determined that designing a hard hat outer shell utilizing an innovative material, with one or more of the properties discussed herein, allows for the design of an innovative hard hat with the improved performance discussed herein, including improved structural performance and/or decreased bulk/weight/thickness. In specific embodiments, Applicant has determined that Milwaukee Material has one or more of the properties discussed herein in relation to FIGS. 2-3 .

As noted above, Applicant has determined that utilization of the materials discussed herein allows for an improved hard hat outer shell while still providing the needed structural performance. In various embodiments, the outer shell includes a minimum wall thickness. In some embodiments the total weight of the outer shell is less than a maximum weight. In such embodiments, the hard hat shell has these thicknesses and/or weights while providing one or more of the structural characteristics discussed herein.

FIGS. 2 and 3 show the yield strain and tensile strength of an outer shell Milwaukee Material are plotted relative to Material A and Material B. Tensile properties of all materials were measured according to ASTM standard D638 under testing conditions including a temperature of 23° C. (±2° C.) and a rate of 0.5 inches/minute. In a specific embodiment, Milwaukee Material has a yield strain greater than 9%. In a specific embodiment, Milwaukee Material has a yield strain between 9% and 17%, specifically between 12% and 16% and more specifically between 13% and 15%. In a specific embodiment, Milwaukee Material has a tensile strength greater than 35 megapascal (MPa). In a specific embodiment, Milwaukee Material has a tensile strength between 35 and 75 MPa, specifically between 45 and 65 MPa and more specifically between 50 and 60 MPa.

Referring to FIGS. 4-6 , the tensile properties of Milwaukee Material, Material A and Material B were measured according to a modified ASTM standard D638 procedure under testing conditions including a temperature of −30° C. (±2° C.) and a rate of 1 meter/minute are shown. FIG. 4 is a stress-strain curve of one embodiment of Milwaukee Material showing the strain to failure or the maximum amount a material is able to stretch before breaking. In a specific embodiment, Milwaukee Material has a strain to failure between 17% and 85%, specifically between 50% and 80% and more specifically between 70% and 78%. In a specific embodiment, Milwaukee Material has a yield strain between 5% and 20%, specifically between 8% and 14% and more specifically between 10% and 12%. In a specific embodiment, Milwaukee Material has a tensile strength between 65 and 105 MPa, specifically between 75 and 95 MPa and more specifically between 82 and 92 MPa.

Referring to FIGS. 7-8 , the impact strength of Milwaukee Material, Material A and Material B were measured using a notched izod impact strength (i.e., total amount of energy required to initiate and propagate a crack in the material) according to ASTM standard D256 Method A under various conditions. FIG. 7 shows the relative notched izod impact strength of Milwaukee Material, Material A and Material B under testing conditions including a temperature of 23° C. (±2° C.). In a specific embodiment, Milwaukee Material has an impact resistance greater than 450 joules/meter. In a specific embodiment, Milwaukee Material has an impact resistance between 450 and 900 joules/meter, specifically between 600 and 800 joules/meter and more specifically between 700 and 750 joules/meter. FIG. 8 shows the relative notched izod impact strength of Milwaukee Material, Material A and Material B under testing conditions including a temperature of −30° C. (±2° C.). In a specific embodiment, Milwaukee Material has an impact resistance between 160 and 800 joules/meter, specifically between 500 and 700 joules/meter and more specifically between 650 and 680 joules/meter.

Referring to FIGS. 9 , the multi-axial impact toughness (i.e., the amount of energy to initiate a crack in a material) of Milwaukee Material is plotted relative to Material A and Material B. The multi-axial impact toughness of Milwaukee Material, Material A and Material B were measured according to ISO 6603-2 under testing conditions including a temperature of −30° C. (±2° C.) and a rate of 4.4 meters/second. In a specific embodiment, Milwaukee Material has an impact toughness greater than 27 joules. In a specific embodiment, Milwaukee Material has an impact toughness between 27 and 90 joules, specifically between 60 and 80 joules and more specifically between 65 and 75 joules.

It should be understood that the figures illustrate the exemplary embodiments in detail, and it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. The construction and arrangements, shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

Various embodiments of the invention relate to any combination of any of the features, and any such combination of features may be claimed in this or future applications. Any of the features, elements or components of any of the exemplary embodiments discussed above may be utilized alone or in combination with any of the features, elements or components of any of the other embodiments discussed above.

For purposes of this disclosure, the term “coupled” means the joining of two components directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. 

What is claimed is:
 1. A hard hat, comprising: an outer shell, the outer shell comprising: an exterior surface; an interior surface defining a cavity sized to receive a head of an operator; a brim portion defining a lower circumference extending along the exterior surface; an impact protection layer positioned within the cavity; wherein the outer shell is formed from a material that includes a yield strain greater than 9%.
 2. The hard hat of claim 1, wherein the outer shell material includes a yield strain between 13% and 15%.
 3. The hard hat of claim 1, wherein the outer shell material includes a strain to failure greater than 17%.
 4. The hard hat of claim 3, wherein the outer shell material includes a strain to failure between 70% and 80%.
 5. The hard hat of claim 1, wherein the outer shell material includes a notched izod impact strength greater than 450 joules/meter.
 6. The hard hat of claim 5, wherein the notched izod impact strength of the outer shell material is between 700 and 750 joules/meter.
 7. The hard hat of claim 1, wherein the outer shell material includes a tensile strength between 50 MPa and 60 MPa.
 8. The hard hat of claim 1, wherein the outer shell material is a polymer material.
 9. A hard hat, comprising: a shell formed from a rigid material, the shell comprising: an exterior surface; an interior surface defining a cavity configured to receive a head of an operator; a crown portion positioned in a central area of the hard hat surrounding a center point; a bottom portion defining a lower circumference extending along the exterior surface; wherein the shell material includes a tensile strength of greater than 35 MPa.
 10. The hard hat of claim 9, wherein the shell material includes a tensile strength between 50 MPa and 60 MPa.
 11. The hard hat of claim 9, wherein the shell material includes a yield strain greater than 9%.
 12. The hard hat of claim 9, wherein the shell material is a rigid polymer material.
 13. The hard hat of claim 9, wherein the shell material includes a strain to failure greater than 17%.
 14. The hard hat of claim 9, wherein the shell material includes a notched izod impact strength greater than 160 joules/meter.
 15. The hard hat of claim 14, wherein the shell material includes a notched izod impact strength between 650 and 680 joules/meter.
 16. The hard hat of claim 9, wherein the outer shell material includes a multi-axial impact toughness greater than 27 joules.
 17. A hard hat, comprising: an outer shell formed from a rigid material, the outer shell comprising: an exterior surface; an interior surface defining a cavity configured to receive a head of an operator; a crown portion positioned in a central area of the hard hat surrounding a center point; a bottom portion defining a lower circumference extending along the exterior surface; an impact protection layer positioned within the cavity; wherein the outer shell material includes a multi-axial impact toughness greater than 27 joules.
 18. The hard hat of claim 17, wherein the multi-axial impact toughness of the outer shell material is between 65 and 75 joules.
 19. The hard hat of claim 17, wherein the outer shell material includes a tensile strength greater than 9% and a tensile strength greater than 35 MPa.
 20. The hard hat of claim 17, wherein the outer shell material includes a strain to failure greater than 17%. 